Grianán Ailigh
On the road from Letterkenny to Derry is Grianán Ailigh, a circular fort whose origins date to around 1700 BC. It is said to have been built by Dagda, an ancient king of the Tuatha De Danann. Burt Castle, a 16th century stronghold, can be seen in the distance.
Grianán Ailigh, (In English, The Grianan of Aileach) is a group of historic monuments in County Donegal, Ireland built on the hill of Grianán which is 244 meters high. Most writers have identified the site as being the great “royal fort” of Aileach. The main monument is that of an Iron Age stone fortress. It is generally accepted to be the seat of the Kingdom of Aileach although the true capital is now believed to lie further to the east. The Grianán was a historical center of culture and politics during the rule of early Irish chieftains (c. 800 B.C.E.-1200 C.E.).
The Grianán is located on the western edge of a small group of hills that lie between the upper reaches of Lough Swilly and Lough Foyle. Although the hill is comparatively not that high, the summit dominates the neighbouring counties of Londonderry, Donegal and Tyrone. Located at the edge of the Inishowen peninsula, it is 11.25 kilometers northwest of the ecclesiastical site of Derry.
Both sites histories are closely linked. There is much legend and historical material related to the Grianán of Aileach. The Irish annals record its destruction in 1101. The main monument on the hill is a stone cashel, restored in the nineteenth century, but probably built in the eighth century A.D. The summit's use as an area of settlement may go back much further. A tumulus at the Grianán may date back to Neo lithic age and a covered well was found nearby the cashel in the early nineteenth century.